Integration techniques for MIM or MIP capacitors with flash memory and/or high-κ metal gate CMOS technology
Some embodiments of the present disclosure relate to an integrated circuit (IC) arranged on a semiconductor substrate, which includes a flash region, a capacitor region, and a logic region. An upper substrate surface of the capacitor region is recessed relative to respective upper substrate surfaces of the flash and logic regions, respectively. A capacitor, which includes a polysilicon bottom electrode, a conductive top electrode arranged over the polysilicon bottom electrode, and a capacitor dielectric separating the bottom and top electrodes; is disposed over the recessed upper substrate surface of the capacitor region. A flash memory cell is disposed over the upper substrate surface of the flash region. The flash memory cell includes a select gate having a planarized upper surface that is co-planar with a planarized upper surface of the top electrode of the capacitor.
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The present application claims priority to U.S. provisional application filed on Jan. 30, 2015, which has an Application No. 62/110,002 and is entitled “HIGH CAPACITANCE AND/OR HIGH VOLTAGE CAPACITOR TECHNIQUES TO INTEGRATE WITH HIGH-k METAL GATE CMOS TECHNOLOGY”, the contents of which are incorporated herein in their entirety.
BACKGROUNDThe semiconductor manufacturing industry has experienced exponential growth over the last few decades. In the course of semiconductor evolution, the minimum feature sizes for semiconductor devices has decreased over time, thereby helping to increase the number of semiconductor devices per unit area on successive generations of integrated circuits (ICs). This device “shrinkage” allows engineers to pack more devices and more corresponding functionality onto newer generations of ICs, and is consequently one of the underlying drivers of the modern digital age. Another advancement that has helped improve the functionality of ICs has been to replace traditional polysilicon gates with metal gates, and to replace traditional silicon dioxide gate dielectrics with so called high-κ dielectrics. Whereas silicon dioxide has a dielectric constant of approximately 3.9, high-κ dielectrics have a dielectric constant of more than 3.9, which helps to reduce gate leakage and allows faster switching for transistors.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The present disclosure provides many different embodiments, or examples, for implementing different features of this disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
A trend in the semiconductor manufacturing industry is to integrate different types of semiconductor devices onto a single integrated circuit (IC). Such integration can advantageously lower manufacturing costs, simplify manufacturing procedures, and increase performance of the final product. Embedded flash memory, which can integrate flash memory cells with other types of semiconductor devices, is one example of a technology where integration is advantageous. Traditional flash memory cells and corresponding logic devices are formed with polysilicon gates insulated by silicon dioxide. As semiconductor feature sizes get smaller, however, the logic devices of such embedded flash memory devices are reaching performance limits. Accordingly, high κ metal gate (HKMG) technology has become one of the front runners for the logic devices in the next generation of embedded flash memory devices. HKMG technology employs a metal gate separated from the underlying substrate by a material with a high dielectric constant κ (relative to silicon dioxide). The high κ dielectric reduces leakage current and increases the maximum drain current, and the metal gate mitigates the effects of Fermi-level pinning and allows the gate to be employed at lower threshold voltages. Further, the high κ dielectric and the metal gate collectively reduce power consumption. Thus, the aim for future generations of embedded flash memory is to integrate flash cells having polysilicon gates with HKMG logic devices.
Recent attempts to form such embedded flash memory devices have suffered from shortcomings. For example, one recent challenge arises from the fact that embedded flash memory devices and HKMG technology has been incompatible with polysilicon-insulator-polysilicon (PIP) and polysilicon-insulator-metal (PIM) capacitor technologies until now. In particular, this incompatibility has stemmed from a lack of sufficient height or thickness to form the PIP/PIM capacitor because of the processing techniques used for flash and HKMG. For example, in a traditional HKMG replacement gate process (RPG), a chemical mechanical polishing (CMP) operation usually planarizes all features to a height corresponding to an upper surface of a sacrificial polysilicon gate of the logic device. This CMP process would result in a PIP or PIM capacitor being squeezed too thin vertically, such that there is insufficient vertical space to provide upper and lower capacitor electrodes which are separated from one another by a capacitor dielectric in a reliable manner.
Accordingly, the present disclosure is directed to improved methods of semiconductor manufacturing wherein a capacitor region of the substrate over which a PIP or PIM capacitor is to be formed is recessed relative to flash and HKMG regions. This allows an increased overall height or thickness for the PIP or PIM capacitors when such capacitors are integrated on chip with flash and HKMG circuits.
As will be appreciated in greater detail further herein, capacitor 116 can take various forms depending on the implementation. The bottom electrode 118 is typically polysilicon, but the top electrode 120 can manifest as doped polysilicon (resulting in capacitor 116 being a PIP capacitor) or can manifest as metal (resulting in capacitor 116 being a PIM capacitor). The first capacitor dielectric 122 can manifest as SiO2, which corresponds to a gate oxide 124 of a pair of split gate flash memory cells in flash region 104; or can correspond to a charge trapping dielectric 126 of the pair of split flash gate cells; or can correspond to a high-κ dielectric 128 of the PMOS and/or NMOS HKMG logic transistors in logic region 108. The second capacitor dielectric 125 can manifest as SiO2, which corresponds to a gate oxide 124 of a pair of split gate flash memory cells in flash region 104, or can correspond to a charge trapping dielectric 126 of the pair of split flash gate cells.
Notably, a planarized upper surface of the capacitor top electrode (120′) is co-planar with a planarized top surface of a select gate (e.g., 136a′) of a flash memory cell, and is also co-planar with a planarized upper surface of a replacement metal gate (e.g., 148′) of the PMOS and/or NMOS HKMG logic transistors. By forming the capacitor 116 on the recessed surface 110, the techniques provided herein allow the capacitor to have a sufficiently large height or thickness such that the bottom electrode 118, top electrode 120, and first and second capacitor dielectrics 122, 125 can operate in a reliable manner.
The illustrated pair of split gate flash cells 130 is made up of a first memory cell 132a and a second memory cell 132b, which are mirror images of one another about an axis of symmetry in some implementations. The pair of split gate flash cells 130 includes two individual source/drain regions 134a, 134b, and a common source/drain region 134c that is shared between the memory cells 132a, 132b. The first and second memory cells include select gates 136a, 136b, respectively and control gates 138a, 138b, respectively, over the cells' respective channel regions. Each select gate and control gate comprises a conductive material, such as a doped polysilicon layer. Gate oxide 124 can typically include SiO2. In some examples, charge trapping dielectric 126 includes a charge trapping silicon nitride layer sandwiched between two silicon dioxide layers to create a three-layer stack collectively and commonly referred to as “ONO.” Other charge trapping dielectrics may include a silicon-rich nitride film or a layer of silicon nanoparticle dots, or any film that includes, but is not limited to, silicon, oxygen, and nitrogen in various stoichiometries.
HKMG transistors 140a, 140b are arranged over the logic region 108. In some embodiments, the high-κ dielectric layer 128 includes a bottom high temperature oxide (HTO) layer 142 formed by exposing the substrate to an elevated temperature (e.g., approximately 1000° C.) during a furnace oxidation process. In some embodiments, the thickness of the HTO layer 142 is between approximately 80 angstroms and 200 angstroms, being approximately 180 Angstroms in some embodiments. A high κ dielectric layer 144 is arranged over the HTO layer 142. In some embodiments, the high κ dielectric layer 144 comprises HfO (hafnium oxide), HfSiO (hafnium silicon oxide), HfAlO (hafnium aluminum oxide), or HfTaO (hafnium tantalum oxide). An etch-stop layer (ESL) 146 is arranged over the high-κ dielectric layer 144, and replacement metal gate electrode 148 overlies ESL 146. An interlayer dielectric (ILD) 152, such as a low-κ dielectric layer, overlies the substrate 102.
The method starts at 1200, where a semiconductor substrate is provided. The substrate includes a flash memory region, a capacitor region, and a logic region. STI regions in the substrate isolate the flash memory region, the capacitor region, and the logic region from one another.
At 1202, an upper substrate surface of capacitor region is recessed relative to respective upper substrate surfaces of flash memory and logic regions, respectively.
At 1204, a doped region is formed in the capacitor region of the substrate to correspond to a capacitor plate.
Three separate flows to form a flash memory device, HKMG transistor, and PIP or PIM capacitor are illustrated as stemming from 1204. The first flow begins at 1208, where a first dielectric layer and a first poly layer are formed over the flash memory and capacitor regions to correspond to a select gate of flash memory and a capacitor bottom electrode. In 1210, first dielectric and first poly layers are formed over the flash memory and capacitor regions to correspond to a flash select gate and a capacitor bottom electrode. In 1212, a second poly layer is formed over the second dielectric to form a flash control gate. In 1214, a third dielectric is formed over the capacitor bottom electrode and logic region. In 1216, a third poly layer is formed over the third dielectric to establish a top capacitor electrode and logic gate. In 1218, an ILD is formed over flash memory region, capacitor region, and logic region, and CMP is performed to make upper surfaces of select gate, top capacitor electrode, and logic gate co-planar.
The second flow begins at 1220, where a first dielectric layer and first poly layer are formed over flash memory and capacitor regions to correspond to a flash select gate and capacitor bottom electrode. In 1222, a second dielectric, which is a charge trapping dielectric, is formed over the flash region on sidewalls of the select gate and over the first poly layer. In 1224, a second poly layer is formed over the second dielectric to form flash control gate and top capacitor electrode. In 1226, a third dielectric is formed over the logic region. In 1228, a third poly layer is formed over third dielectric to form logic gate. In 1230, an ILD is formed over the flash memory region, capacitor region, and logic region; and CMP is performed to make upper surfaces of select gate, top capacitor electrode, and logic gate co-planar.
The third flow begins at 1232, where a first dielectric and first poly layer are formed over flash memory region to correspond to flash select gate. In 1234, a second dielectric, which is a charge trapping dielectric, is formed over the flash region on sidewalls of the select gate and over capacitor region. In 1236, the second poly layer is formed over the second dielectric to form a flash control gate and a bottom capacitor electrode. In 1238, a third dielectric is formed over the logic region and over the bottom capacitor electrode. In 1240, a third poly layer is formed over the third dielectric to form a logic gate and a top capacitor electrode. In 1242, an ILD is formed over the flash memory region, capacitor region, and logic region; and CMP is performed to make upper surfaces of select gate, top capacitor electrode, and logic gate co-planar.
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Accordingly, some embodiments of the present disclosure relate to an integrated circuit (IC) arranged on a semiconductor substrate, which includes a flash region, a capacitor region, and a logic region. An upper substrate surface of the capacitor region is recessed relative to respective upper substrate surfaces of the flash and logic regions, respectively. A capacitor, which includes a polysilicon bottom electrode, a conductive top electrode arranged over the polysilicon bottom electrode, and a first capacitor dielectric separating the bottom and top electrodes; is disposed over the recessed upper substrate surface of the capacitor region. A flash memory cell is disposed over the upper substrate surface of the flash region. The flash memory cell includes a select gate having a planarized upper surface that is co-planar with a planarized upper surface of the top electrode of the capacitor.
Other embodiments relate to an integrated circuit (IC). The IC is arranged on a semiconductor substrate, which includes a flash region, a capacitor region, and a logic region. An upper substrate surface of the capacitor region is recessed relative to respective upper substrate surfaces of the flash and logic regions, respectively. A first capacitor is disposed over the recessed upper substrate surface of the capacitor region. The first capacitor includes a polysilicon bottom electrode, a polysilicon or metal top electrode arranged over the polysilicon bottom electrode, and a first capacitor dielectric separating the bottom and top electrodes. A second capacitor is disposed over the recessed upper substrate surface of the capacitor region, and is stacked in parallel with the first capacitor. The second capacitor includes a doped region in the capacitor region of the semiconductor substrate, the polysilicon bottom electrode, and a second capacitor dielectric separating the doped region from the polysilicon bottom electrode.
Still other embodiments relate to a method. In this method, a semiconductor substrate, which includes a flash memory region, capacitor region, and logic region, is received. An upper substrate surface of the capacitor region is recessed relative to the flash memory region and logic region. A poly-insulator-poly (PIP) or poly-insulator-metal (PIM) capacitor is formed on the recessed upper substrate surface of the capacitor region.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
Claims
1. An integrated circuit (IC), comprising:
- a semiconductor substrate including a flash region, a capacitor region, and a logic region, wherein an upper substrate surface of the capacitor region is recessed relative to respective upper substrate surfaces of the flash and logic regions, respectively;
- a capacitor disposed over the recessed upper substrate surface of the capacitor region, the capacitor including: a polysilicon bottom electrode, a conductive top electrode arranged over the polysilicon bottom electrode, and a first capacitor dielectric separating the bottom and top electrodes; and
- a flash memory cell disposed over the upper substrate surface of the flash region, the flash memory cell including a select gate having a planarized upper surface that is co-planar with a planarized upper surface of the top electrode of the capacitor.
2. The IC of claim 1, further comprising:
- a doped region of semiconductor substrate directly under the polysilicon bottom electrode; and
- a second capacitor dielectric separating the doped region from the polysilicon bottom electrode;
- wherein the doped region is ohmically coupled to the top electrode such that the doped region and top electrode collectively act as a capacitor plate of the capacitor.
3. The IC of claim 2, wherein the second capacitor dielectric differs from the first capacitor dielectric.
4. The IC of claim 1, further comprising:
- a transistor disposed over the upper substrate surface of the logic region, the transistor including a metal gate having a planarized upper surface that is co-planar with both the planarized upper surface of the top electrode of the capacitor and the planarized upper surface of the select gate of the flash memory cell.
5. The IC of claim 4, wherein the conductive top electrode is a metal electrode made of the same material as the metal gate of the transistor.
6. The IC of claim 4, wherein the first capacitor dielectric is the same dielectric as a transistor gate dielectric which separates the metal gate of the transistor from the upper substrate surface of the logic region.
7. The IC of claim 1, wherein the conductive top electrode is a polysilicon electrode.
8. The IC of claim 1, wherein the first capacitor dielectric is a high-k dielectric which has a dielectric constant of greater than 3.9.
9. The IC of claim 1, wherein the flash memory cell comprises:
- a polysilicon select gate arranged over a channel region of a first flash memory cell of a pair of split gate flash memory cells, wherein the polysilicon select gate is separated from the flash region of the substrate by a gate dielectric layer;
- a polysilicon control gate arranged about an outer sidewall of the select gate; and
- a charge trapping dielectric layer separating the control gate from the flash region of the substrate.
10. The IC of claim 9, wherein the charge trapping dielectric layer comprises:
- a first oxide layer abutting an upper surface of the bottom electrode;
- a nitride layer or layer of silicon dots abutting an upper surface of the first oxide layer; and
- a second oxide layer abutting an upper surface of the nitride layer or layer of silicon dots, wherein the second oxide layer has an upper surface that abuts a corresponding lower surface of the top electrode.
11. The IC of claim 1, further comprising:
- a shallow trench isolation (STI) region disposed within the semiconductor substrate and separating the capacitor region from the flash region, wherein an upper surface of the STI region extends to a first height above the upper substrate surface nearest the flash region and resides at a second height below the upper substrate surface nearest the capacitor region.
12. An integrated circuit (IC), comprising:
- a semiconductor substrate including a flash region, a capacitor region, and a logic region, wherein an upper substrate surface of the capacitor region is recessed relative to respective upper substrate surfaces of the flash and logic regions, respectively;
- a first capacitor disposed over the recessed upper substrate surface of the capacitor region, the first capacitor including: a polysilicon bottom electrode, a polysilicon or metal top electrode arranged over the polysilicon bottom electrode, and a first capacitor dielectric separating the bottom and top electrodes;
- a second capacitor disposed over the recessed upper substrate surface of the capacitor region and stacked in parallel with the first capacitor, the second capacitor including: a doped region in the capacitor region of the semiconductor substrate, the polysilicon bottom electrode, and a second capacitor dielectric separating the doped region from the polysilicon bottom electrode; and
- a flash memory cell disposed over the upper substrate surface of the flash region, the flash memory cell including a gate electrode having a planarized upper surface that is co-planar with a planarized upper surface of the top electrode of the first capacitor.
13. The IC of claim 12, further comprising:
- a transistor disposed over the upper substrate surface of the logic region, the transistor including a metal gate having a planarized upper surface that is co-planar with the planarized upper surface of the top electrode of the first capacitor.
14. The IC of claim 13, wherein the first and second capacitor dielectrics are SiO2 layers.
15. The IC of claim 13, wherein the first capacitor dielectric is a high-k dielectric layer and the second capacitor dielectric is an oxide layer or a charge-trapping layer.
16. The IC of claim 13, wherein the first capacitor dielectric is a charge trapping layer and the second capacitor dielectric is an oxide layer.
17. The IC of claim 13, wherein the upper substrate surfaces of the flash and logic regions are co-planar with one another.
18. A method, comprising:
- receiving a semiconductor substrate that includes a flash memory region, capacitor region, and logic region;
- recessing an upper substrate surface of the capacitor region relative to the flash memory region and logic region;
- forming a poly-insulator-poly (PIP) or poly-insulator-metal (PIM) capacitor on the recessed upper substrate surface of the capacitor region;
- forming a flash memory cell on the flash memory region;
- forming a high-k metal gate (HKMG) transistor on the logic region; and
- performing a planarization to make an upper surface of a top electrode of the PIP or PIM capacitor co-planar with an upper surface of a gate electrode of the memory cell or with an upper surface of a gate electrode of the HKMG transistor.
19. The method of claim 18, wherein the flash memory cell includes a select gate, and performing the planarization makes the upper surface of the top electrode of the PIP or PIM capacitor co-planar with both the upper surface of the select gate and the upper surface of the gate electrode of the HKMG transistor.
20. The IC of claim 1, wherein the first capacitor dielectric has an uppermost surface which is positioned a first depth below the upper substrate surfaces of the flash and logic regions.
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Type: Grant
Filed: Sep 11, 2015
Date of Patent: Feb 14, 2017
Patent Publication Number: 20160225846
Assignee: Taiwan Semiconductor Manufacturing Co., Ltd. (Hsin-Chu)
Inventors: Harry-Hak-Lay Chuang (Zhubei), Yu-Hsiung Wang (Zhubei), Chen-Chin Liu (Hsinchu)
Primary Examiner: Earl Taylor
Application Number: 14/851,357
International Classification: H01L 27/108 (20060101); H01L 49/02 (20060101); H01L 27/115 (20060101);